Electrode active material for secondary battery and method for preparing the same

Abstract

The disclosure relates to an electrode active material including: (a) first particulate of a metal (or metalloid) oxide alloyable with lithium; and (b) second particulate of an oxide containing lithium and the same metal (or metalloid) as that of the metal (or metalloid) oxide, and to a secondary battery including the electrode active material. When the electrode active material is used as an anode active material, reduced amounts of an irreversible phase such as a lithium oxide or a lithium metal oxide are produced during initial charge-discharge of a battery since lithium is already contained in the second particulate before the initial charge-discharge, and thus a dead volume on the side of the cathode can be minimized and a high-capacity battery can be fabricated.

The invention claimed is: 
     
       1. An electrode active material comprising:
 a first particulate of a metal (or metalloid) oxide alloyable with lithium; and 
 a second particulate of an oxide containing lithium and the same metal (or metalloid) as that of the metal (or metalloid) oxide, wherein the first particulate has an average particle size (diameter) from 0.1 nm to 5 μm, and the second particulate has an average particle size (diameter) from 0.1 nm to 20 μm. 
 
     
     
       2. The electrode active material according to  claim 1 , wherein the first particulate and the second particulate are mixed in the electrode active material. 
     
     
       3. The electrode active material according to  claim 1 , wherein the first particulate or aggregates of two or more of the first particulates are surrounded by the second particulate. 
     
     
       4. The electrode active material according to  claim 1 , wherein the first particulate and the second particulate are included in a weight ratio of 5:95 to 95:5. 
     
     
       5. The electrode active material according to  claim 1 , wherein a molar ratio of the metal (or metalloid) (M) and oxygen (O) included in the electrode active material, M/O, is 1 or greater. 
     
     
       6. The electrode active material according to  claim 1 , wherein the metal (or metalloid) of the metal (or metalloid) oxide of the first particulate is selected from a group consisting of Si, Sn, Al, Sb, Bi, As, Ge, Pb, Zn, Cd, In, Ga and alloys thereof. 
     
     
       7. The electrode active material according to  claim 1 , wherein the oxide containing the metal (or metalloid) and lithium of the second particulate is selected from a group consisting of Li 2 SiO, Li 2 SnO, Li 4 SiO 4 , Li 2 Si 2 O 5 , Li 6 Si 2 O 7 , Li 2 Si 3 O 7 , Li 8 SiO 6 , Li 2 SnO 3 , Li 5 AlO 4 , LiAlO 2 , LiAl 5 O 8 , LiSbO 3 , LiSb 3 O 8 , Li 3 SbO 4 , Li 5 SbO 5 , Li 7 SbO 6 , LiSb 3 O 8 , Li 0.62 Bi 7.38 O 11.38 , LiBiO 2 , LiBiO 3 , Li 3 BiO 4 , Li 5 BiO 5 , Li 7 BiO 6 , LiBi 12 O 18.50 , LiAsO 3 , Li 3 AsO 4 , Li 4 As 2 O 7 , Li 2 GeO 5 , Li 2 Ge 4 O 9 , Li 2 Ge 7 O 15 , Li 2 GeO 3 , Li 4 Ge 5 O 12 , Li 4 Ge 9 O 20 , Li 4 GeO 4 , Li 6 Ge 2 O 7 , Li 8 GeO 6 , Li 2 PbO 3 , Li 4 PbO 4 , Li 8 PbO 6 , Li 6 ZnO 4 , LiInO 2 , Li 3 InO 3 , LiGaO 2 , LiGa 5 O 8 , and Li 5 GaO 4 . 
     
     
       8. The electrode active material according to  claim 1 , wherein the oxide containing the metal (or metalloid) and lithium of the second particulate is crystalline, amorphous, or both. 
     
     
       9. The electrode active material according to  claim 1 , wherein the electrode active material is an anode active material. 
     
     
       10. A secondary battery comprising the electrode active material according to  claim 1 . 
     
     
       11. The secondary battery according to  claim 10 , which has an initial efficiency of 50% or greater. 
     
     
       12. A method for preparing the electrode active material according to  claim 1 , comprising:
 chemically or mechanically mixing an oxygen-free lithium salt and a metal (or metalloid) oxide alloyable with lithium; 
 heat treating the resulting mixture under an inert atmosphere at a temperature between the melting point of the oxygen-free lithium salt and the boiling point of the oxygen-free lithium salt, or mechanically alloying the resulting mixture; and 
 forming a first particulate of the metal (or metalloid) oxide alloyable with lithium; and a second particulate of an oxide containing lithium and the same metal (or metalloid) as that of the metal (or metalloid) oxide, wherein the first particulate has an average particle size (diameter) from 0.1 nm to 5 μm, and the second particulate has an average particle size (diameter) from 0.1 nm to 20 μm. 
 
     
     
       13. The method for preparing an electrode active material according to  claim 12 , wherein the oxygen-free lithium salt is selected from a group consisting of LiCl, LiBF 4 , LiAlCl 4 , LiSCN, LiSbF 6 , LiPF 6 , LiAsF 6 , LiB 10  Cl 10 , LiF, LiBr and LiI. 
     
     
       14. The method for preparing an electrode active material according to  claim 12 , wherein the metal (or metalloid) of the metal (or metalloid) oxide of the first particulate is selected from a group consisting of Si, Sn, Al, Sb, Bi, As, Ge, Pb, Zn, Cd, In, Ga and alloys thereof. 
     
     
       15. The method for preparing an electrode active material according to  claim 12 , wherein the oxygen-free lithium salt and the metal (or metalloid) oxide are mixed at a weight ratio of 5:95 to 80:20. 
     
     
       16. The method for preparing an electrode active material according to  claim 12 , wherein the chemical mixing comprises: dispersing the metal (or metalloid) oxide in a solution prepared by dissolving the oxygen-free lithium salt in a solvent to prepare a dispersion; and drying the dispersion. 
     
     
       17. The method for preparing an electrode active material according to  claim 12 , wherein the mechanical mixing is performed using a ball mill, a planetary mill, a stirred ball mill or a vibrating mill. 
     
     
       18. The method for preparing an electrode active material according to  claim 12 , wherein the heat treatment is performed at 500-2000 ° C. 
     
     
       19. The method for preparing an electrode active material according to  claim 12 , wherein the mechanical alloying is performed using a ball mill, a planetary mill, a stirred ball mill or a vibrating mill.